This invention relates to permanent magnet synchronous machines, such as motors and generators, having integrated magnetic bearings.
Conventional magnetic bearing systems for motors or generators typically require two magnetic bearings, each of which is mounted on the same shaft. To prevent rotor tilt some synchronous machines utilized two separate windings in the same machine housing, in addition to the magnetic elements required for the motor or generator, to produce radial magnetic action and torque production respectively. However, such systems often require a mechanical thrust bearing or an additional magnetic bearing.
The Preston et al. Pat. No. 5,424,595 discloses an integrated magnetic bearing and switched reluctance rotary electric machine in which separately excitable stator phase windings receive a combination of signals, one of which is a phase winding signal and the other of which is a magnetic bearing signal. The two signals are superimposed on the windings in such a manner as to drive the motor and produce the magnetic force necessary to support the rotor in the absence of a mechanical bearing.
The Ohishi Pat. No. 5,237,229 discloses a magnetic bearing device utilizing a rotating magnetic field. That device includes a rotor which has a number of permanent magnets and is mounted on a central shaft which is connected to the drive shaft for a rotating load of an external device. The stator contains electromagnets which are energized successively so as to produce a rotating magnetic field consisting of polarities arranged to oppose or attract the polarities of the permanent magnets mounted on the rotor so as to support the rotor shaft centrally in the device. The Lyons U.S. Pat. No. 5,578,880 also discloses an active magnetic bearing system in which electromagnet coils in a stator surrounding a rotor are controlled by independent controllers to produce a magnetic bearing supporting the rotor and U.S. Pat. No. 5,202,824 to Chen discloses a proportional integral differentiation arrangement for controlling a magnetic bearing system.